1. Field of the Invention
The present invention relates to a method and apparatus for quantitatively and/or qualitatively assaying an analyte using a durable and storable recordation system.
2. Description of Material Information and Related Materials
Solid phase immuno-assays offer the most specific and sensitive methods for detecting and measuring an unknown material (analyte) in a given sample. While the actual use of these methods in the field is quite limited at present, various versions of solid phase assays have been developed and improvements have been proposed such that the earlier fluid phase immuno-assays (e.g. gel diffusion, precipitation, agglutination) will probably be replaced by a new generation of immuno-assays. Solid phase assays may be more complicated and require more elaborate and complicated technology, but they offer higher sensitivity and are better adapted for quantitative work. The present state of the art and the applicability of solid phase immuno-assays are extensively reviewed in U.S. Pat. Nos. 3,654,090 and 4,299,916.
Briefly, present methods are capable of measuring an unknown analyte provided it is either an antibody to a known antigen or an antigen, i.e., a material to which a specific antibody can bind.
Depending on the nature of the unknown, i.e., whether it is an antibody or an antigen, the specific counterpart (receptor) is affixed onto a solid surface such as the inner wall of a test tube, a dip-stick or beads. The analyte then binds to its solid phase receptor. The presence of the bound analyte and its quantity can then be determined by a labelled molecule (probe) which is either the analyte itself (competitive assay) or an antibody to the analyte ("sandwich" assay). The label can be radioactive (Radio Immuno-assay), enzymatic (Enzyme immuno-assay) or fluorescent (Fluorescence immuno-assay). The solid phase principle facilitates the separation of unbound labelled and unlabelled components of the assay system (antigens and/or antibodies).
Whilst the sensitivity of a solid phase immuno-assay can be tailored to the specific case, and specificity can be easily obtained, assays require certain improvements to make them more reliable, usable and portable. Thus, it would be desirable to:
a) Simplify and stabilize reagents, so that the assay components can be stored inexpensively and for long periods of time.
b) Provide an instantaneous, built-in quality control monitoring system for each of the steps involved since materials can become stale and steps may be improperly performed, thus affecting the final result.
c) Be able to perform differential diagnosis of infectious diseases where a plurality of unknowns can be screened in a single assay. Such a diagnosis would preferably be preformed using a single apparatus with a minimum of steps.
d) Be able to simultaneously assay a plurality of samples for the same unknown, without risk of cross-contamination.
e) Provide an apparatus with which untrained field staff may perform the assays and analyze the results obtained by visual inspection. To accomplish this the assay kits should be storage stable and simple to use. Such kits should include a minimal number of components and should lend themselves to easy filing and record keeping of the unknown, and standard values.
There is known in the art a card system adapted for sequential exposure to the various solutions of an assay procedure. The card itself may be made of polyvinyl, polystyrene, cellulose, nylon or glass. Depending upon the particular material selected, such a card may be suitable for storage for long periods of time.
Using a card configured in the known manner, individual samples to be assayed must be separately applied in a manner such that different samples do not contaminate one another. Even when samples are separately applied, because of the configuration of the card, the processing of the card may result in cross-contamination if more than one sample is applied to different parts of the card. As a result, the possibility of cross-contamination presents a serious obstacle to automated mass-processing. For this reason, the card lends itself more readily to multiple testing of a series of the same samples, rather than to simultaneously performing the same assay procedure on a plurality of samples from different subjects.
Furthermore, because of the configuration of the card, when different parts of the card must be separately processed, special precautions must be taken to prevent undesirable exposure. For example, depending upon the procedure, it may be desirable to subject the portion of the card having the control thereon to a different sequence of exposures. In such cases, special care must be taken to avoid exposure of the control portion, and the shape of the card may make such selective exposure somewhat awkward and difficult.
In addition to the above drawbacks, such cards would become more useful and commercially valuable if their results could be computerized. While results of such assays can, of course, always be manually inputted, it would be very useful if the results could be automatically read off of the card, and be stored in a retrievable manner which permits them to be readily associated with the particular subject from whom the sample (s) was (were) taken, together with any other pertinent information.